MEPS 2 - The Next Stage of Efficiency Regulation for Distribution Transformers Trevor Blackburn School of Electrical Engineering UNSW.

MEPS 2 - The Next Stage of Efficiency Regulation for Distribution Transformers

Trevor BlackburnSchool of Electrical Engineering

UNSW

The Role and Purpose of MEPS Regulations

• Improve power and energy efficiency levels• Reduce electrical energy waste and CO2 emissions• Done by regulating minimum efficiency levels• Applied to locally-manufactured and imported items• Electrical equipment regulated by MEPS include:

– Distribution transformers– Large electrical drives– Air conditioners– Fluorescent ballasts– Compact fluorescents

The MEPS regulation process

• Public domain technical report issued• Discussions with manufacturers and users• Regulatory Impact Statement generated• Australian Standard developed and published• Applications for registration and approval for

specific classes of transformers• Compliance testing process

Distribution Transformer Range

• Single phase and three phase• Ratings: 10 kVA – 3100 kVA (2500 now)• Includes: oil-filled, dry-type and SWER units• MEPS 1

– Introduced in 2004 – Two minimum power efficiency levels specified

• Standard [Regulated minimum levels]• High efficiency [Voluntary levels]

• MEPS 2• Proposed implementation date of no earlier than

– 2012– One regulated minimum efficiency level is specified

• Identical to the MEPS 1 high efficiency level

Why Transformers?

• Network losses are significant– Represent about 5-10% of overall T & D energy

transfer

• Network Transformers – Cause up to 40% of total network losses

• Between the generator and consumer at 400/230 V, electrical energy may pass through: – 2 transmission transformers– 2 or 3 distribution transformers

Distribution losses in Australian utilities2009 [ESAA – EGA data]

7

Transmission & Distribution transformer regulation ?

• Transmission transformers– Usually one-off design– Usually very energy efficient– Very small numbers– Give only limited energy saving benefits

• Distribution transformers– Mass produced to an economic design– Losses may be sacrificed for low capital cost– Very large numbers in use– Potentially large energy saving benefits

Number of utility-owned Distribution Transformers in Australia: 2010

• 33 kV 7,544• 22 kV 213,373• 11 kV and below 337,759• SWER 113,248

• TOTAL 661,934

• Usually relatively lightly loaded (25-30%)• Long life expected

9

Number of privately owned transformers (commerce, industry, mines)

• Difficult to determine• Large numbers of imported units• Based on international numbers, about

25% of utility numbers• Generally shorter life than utility trafos• More heavily loaded:

– About 40-50% on average

Transformer loss and

greenhouse gas mitigation

MEPS for Transformers

AS 2374.1.2 - 2004Power transformers – Part 1.2Minimum efficiency Performance Standards (MEPS) requirements for Distribution Transformers

Specifies minimum (power) efficiency levels for oil and dry-type transformers under specific test conditions

Existing MEPS efficiency LevelsLiquid-immersed transformers

(at 50% rated load)

Existing MEPS Levels Dry-type transformers

[at 50% rated load]

Effect of loading on losses

Targosz_2007(Leonardo)

MEPS 2 Levels

Why do we need to increase MEPS1 efficiency levels to MEPS2?

• Need the most efficient transformers that are available to minimise the effect on climate change

• Power electronic loads on transformers will increase losses due to harmonic content:– Increasing harmonic levels arise from use of:

• Adjustable speed drives (IGBT switching)• Switch mode power supplies (Computers and IT equipment)• Compact fluorescent lamps• Any other non-linear loading

– Transformer losses scale as the square of harmonic number

• May require de-rating of transformers in some applications to avoid overheating

• K-factor transformers

1000 kVA oil filled transformer

• Daily load cycle– 8 hours @ full load, unity PF– 6 hours @ 50% load, unity PF– 6 hours @ 25% load, unity PF– 4 hours @ no load

• MEPS 1 power efficiency = 99.27%• MEPS 2 power efficiency = 99.37%

Energy savings with MEPS 2

Energy savings potential

• MEPS 1efficiency– Daily energy efficiency: 99.07%– Daily energy loss: 117 kWh

• MEPS 2 efficiency– Daily energy efficiency: 99.24% – Daily energy loss: 100 kWh

• Daily energy saving with MEPS2 17 kWh• Annual saving with MEPS 2: 6.21 MWh• Annual CO2 saving: 6.42 tonnes

Effect of non-linear loads

• Both core loss and load loss are increased by harmonic frequency content of the load current and/or supply voltage

• Core loss– Hysteresis loss scales as (f)1.8

– Eddy current loss scales as (f)2

• Copper eddy current loss scales as (f)2

20

Adjustable speed induction drive harmonics

21

CFL Current Harmonics

Effect of harmonic loss 150 kVA transformer supplying PCs

Requires de-rating to 125 kVA to maintain normal life

Can the efficiency levels of transformers be increased?

• What are the ultimate efficiency limits?• What are the manufacturing constraints?• New materials?• What are the operational constraints?• Industrial use and impact on losses• Total life cycle cost of the transformer

The ultimate efficiencies[US DOE determination : MAX-TECH levels]

25

Comparison of MEPS1 with other international efficiencies for liquid immersed three phase transformers

Efficiency Comparison: 3 phase liquid

97.8

98

98.2

98.4

98.6

98.8

99

99.2

99.4

99.6

99.8

100

50 100 160 250 400 630 1000 1600 2500

Transformer rating (kVA)

Po

we

r e

ffic

ien

cy (

%)

MEPS1

US benchmark

US proposed

EU existing

EU proposed

Japan top runner

26

Comparison of MEPS1 [12 and 24 kV] with other international efficiencies for dry-type three phase transformers

Efficiency comparison: 3 phase Dry type (12 kV)

96.5

97

97.5

98

98.5

99

99.5

100

50 100 160 250 400 630 1000 1600 2500

Transformer Rating (kVA)

Tra

nsf

orm

er e

ffic

ien

cy (

%)

MEPS1 12 kV

US Benchmark

US Proposed

EU HD528

Japan top runner

MEPS1 24kV

Australian ESI Aug 07 27

Comparison of MEPS1 And MEPS2 liquid immersed transformer efficiencies with international standards

Oil Tx comparison

97.8

98

98.2

98.4

98.6

98.8

99

99.2

99.4

99.6

99.8

100

1 2 3 4 5 6 7 8 9

MEPS1

US benchmark

US prop

EU C-C'

EU pr

Japan

MEPS2

New MEPS comparison

Australian ESI Aug 07 29

MEPS1 and MEPS2 efficiencies for all transformer types and ratings

MEPS1 and MEPS2 Transformer Efficiencies

96

96.5

97

97.5

98

98.5

99

99.5

100

10 16 25 50 25 63 100 200 315 500 750 1000 1500 2000 2500

Transformer Rating (kVA)

Po

wer

Eff

icie

ncy

@ 0

.5 p

u (

%)

Oil 1ph_MEPS1

Oil 3ph_MEPS1

Oil 1ph_MEPS2

Oil 3ph_MEPS2

Dry(12kV) 1ph_MEPS1

Dry(12kV) 3ph_MEPS1

Dry(12kV) 1ph_MEPS2

Dry(12kV) 3ph_MEPS2

30

Increase in transformer numbers and installed capacity for the 30 year modelling period [2006 – 2036].

Increase in Transformer Number and capacity 2006-20036

0

200000

400000

600000

800000

1000000

1200000

1400000

6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36

Year

Nu

mb

er a

nd

MV

A

Utility Tx no.

Utility Tx MVA

Private Tx no.

Private Tx MVA

31

Annual loss of the three phase oil-immersed transformers with MEPS1 and MEPS efficiency and the difference in annual loss [at 25% load]

Annual energy loss @ 25% load for 3 ph oil units with MEPS1 and MEPS2

0

5000

10000

15000

20000

25000

30000

35000

40000

45000

25 63 100 200 315 500 750 1000 1500 2000 2500

Rating (kVA)

En

erg

y lo

ss (

kWh

)

3 ph MEPS1

3 ph MEPS2

MEPS1-MEPS2

Timeline for MEPS 2

• Dec/Jan2008: Broad elements of new standard containing revised figures

• April 2012: Likely Public Comment Draft of new Standard to be produced

• 2013: MEPS 2 to be implemented no earlier than this

33

Efficiency determination

• NATA registered labs for MEPS for Transformers

• TCA (Sydney)• CalTest (Port Elliott, SA)

• CalTest also test Motors to MEPS

Australian ESI Aug 07 34

Manufacturer Tests

• Australian Manufacturers perform loss measurements and efficiency determination as a type test.

• Main manufacturers for utilities are– Wilsons (Wodonga)– Schneider (Benalla)– Tyree (Mittagong)– ABB (Brisbane and Perth)– TMC (Melbourne)– Ampcontrol (Newcastle)

Australian ESI Aug 07 35

Imported transformers

• Very large numbers• Mainly for the private sector• Difficulty in regulating• Testing is difficult because of size• Need mobile test sets

– Caltest have mobile facility– Excite from LV side– Problems with OHS constraints

36

Efficiency determination

• Method used in the Standard is from the main power trafo standard: based on loss compliance tests

• Requires only 1-2% accuracy in loss determination

• But efficiency is specified to a 0.01% variation• Uncertainty of the efficiency determination is

thus questionable• US Dept of Energy has a much more rigorous

test method specified

Conclusions

• Transformers are a significant contribution to overall network loss

• There is significant potential for reduction of transformer losses

• Modern load types increase losses due to the high harmonic content

• Harmonics should be included in some form in testing

• Testing methods as specified need some improvement